If you are using Maya 6 and want to use this background image why dont you take advantage of Mayas IBL (Image Based Lighting) option. Right now the model needs sorting texture wise too, as its looking too much like a plastic kit. Get some good lizard reference such as Iguanas and Komodo Dragons and go from there.
I dont wanna sound too harsh but this is a c+c forum afterall., and the only way to see your mistakes is have others point them out.

Cheers
_J